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Max Planck and Albert Einstein. Planck (left, 1858-1947) was a German physicist whose work led to the development of quantum theory. Einstein (1879-1955), a German- Swiss physicist, put forward relativity theory. In 1900, Planck proposed that radiation is emitted in discrete packets (quanta). This marked the start of modern physics. He received the Nobel Prize for physics in 1918. Einstein won this prize in 1921 for his 1905 paper on the photoelectric effect, the liberation of electrons from matter due to electromagnetic radiation. He also proposed the theories of special and general relativity, which changed our ideas about space and time.